The present invention relates to roller skates, and more particularly to in-line roller skates with flexible bases.
Conventional in-line roller skates include an upper boot secured to or integrally formed with a rigid or semi-rigid base. The base, in turn, is secured along its length, including at heel and toe ends, to a rigid frame. A plurality of wheels is journaled along a common longitudinal axis between the sidewalls of the frame. During use, the skater alternatingly strokes on the left and right skates, thrusting off of one skate while gliding on the opposing skate. The ability to fully complete a thrust and thereby achieve maximum forward momentum is limited, however, because of the rigid frame being secured to the heel and toe of the skater""s foot.
Because of the rigid, inflexible securement of the frame and base of such skates, a skater attempting to achieve optimal speed during skating may adopt a skating stroke that does not entail plantarflexing of his or her ankle during the push-off phase of the stroke. The term xe2x80x9cplantarflexxe2x80x9d refers to the rotation of the foot relative to the leg within a plane defined by the leg, where the forefoot moves distally relative to the leg. By avoiding plantarflexion at the ankle, all skate wheels remain on the ground, with the skate base and frame parallel to the ground. The skate thus does not pivot significantly on the forwardmost wheel. Alternately, a skater may adopt a stroke style entailing plantarflexion of his or her ankle during the skate stroke, allowing the forefoot to move distally of the leg, thereby allowing the calf muscles to generate more power during the skate stroke. Due to the rigid nature of the frame and base however, this causes the skater""s ankle to elevate excessively off the ground, and may be uncomfortable for the skater. This also entails excessive movement of the skater""s upper body and legs, and entails excess wear of the front wheel.
In-line skates with wheels supported on first and second separate frame sections, secured beneath the toe and heel of the skate such that the foot can flex during the skating stroke, have been proposed. For example, U.S. Pat. No. 5,634,648 discloses a skate including a boot having a rigid toe portion pivotally coupled at the lateral sides of the foot to a rigid heel portion. A first frame segment supporting two wheels is secured beneath the toe section and a second frame segment supporting two additional wheels is secured beneath the heel section. A tab extends rearwardly from the base of the toe section and is received within a corresponding slot formed in the base of the heel section. During use, the skater is able to flex the foot at the sidewall pivot point of the upper, with the tab flexing along its length, so that the heel and rear frame section can elevate off of the ground. While permitting flexion of the foot, flexion is not centralized or primarily occurring at the metatarsal head of the skater""s foot, as is anatomically preferred. Thus flexing may be uncomfortable. Additionally, because the boot flexes rearwardly of the front frame and wheels, an unstable platform is provided by the forward segment of the frame during thrusting with the heel elevated. Further, because the two frame segments are separated and uncoupled at all times, there is no lateral rigidity of the frame, even when both frame sections are on the ground. Thus, except to the limited extent provided by the pivot joints between the heel and toe sections of the upper and the forward to rearward tab, there is no torsional rigidity of the skate, as would be desired for straight tracking of the skate.
An alternate flexing skate has been proposed in European Patent Application No. EP 0 778 058 A2. A skate is disclosed having an upper boot with a separate toe segments that is slidably received within the forward end of a rear boot segment and which is pivotally joined to the rear boot segment immediately below the base of the skate. Forward and rearward frame sections are secured beneath the forward and rearward segments of the boot. The rear ends of the sidewalls of the forward frame section overlap the forward ends of the sidewalls of the rear frame section. A second pivot pin is secured through aligned apertures in the forward frame section sidewalls and through corresponding slots in the overlapped sidewalls of the rear frame section. During use, the boot pivots to allow the foot to flex during thrusting, with the slotted rearward frame section moving on the second pivot pin retained by the forward frame section. Thus, a limited degree of flexure is provided, with the pivotal coupling of the frame segments also providing a degree of lateral stability and torsional stiffness.
The degree of flexion of such a skate disclosed in the European ""058 application is limited, however, by the relatively short length of the slots formed in the rearward frame section. Further, the upper or lower positioning of the rear end of the skate is controlled solely by force applied by the user""s foot and leg. During the portion of the skating stroke where the user would desire the wheels to be commonly aligned on the ground in a flat line, the rear of the skate may thus undesirably bump upwardly and downwardly. An alternate embodiment of a skate disclosed in the same European ""058 application has a rigid full-length frame and an unsecured rear boot portion which can be lifted off of the frame for flexure during the stroke. However, there is no provision for laterally stabilizing the heel of the boot relative to the frame, such that undesired torsional or lateral movement of the boot relative to the frame may be encountered. Additionally, as in the segmented frame embodiment, the heel may lift undesirably from the frame at inappropriate times.
The present invention provides a roller skate having a shoe portion for receiving a skater""s foot and a base having an upper surface securable to an underside of the shoe portion for supporting the received skater""s foot. The base includes a heel region and a forefoot region, the forefoot region having a metatarsal head portion. A frame is secured to an underside of the base at least below the forefoot region of the base such that the base can flex intermediate of the forefoot region and heel region during skating to permit elevation of the skater""s heel. The frame extends below the base and rotatably receives a plurality of wheels. At least one forward wheel is disposed below the forefoot region of the base, and at least one rearward wheel is disposed below the heel region of the base. The metatarsal head portion of the base defines a stress-concentrating contour that focuses flexure of the base at the metatarsal head portion.
In a further aspect of the present invention, the skate includes a biasing member coupled to the base to bias the heel region of the base to a lower position, in which the heel region of the base bears on the frame, the rearward wheel, and the ground. The biasing member preferably exerts a downward pre-load on the heel region of the base when the heel region is in the lower position.
In a first preferred embodiment of the present invention, the frame of the skate includes a forward segment secured to an underside of the base below the forefoot region of the base, and a rearward segment secured to the underside of the base below the heel region. The forward segment mounts the at least one forward wheel below the forefoot region of the base, while the rearward segment mounts the at least one rearward wheel below the heel region of the base. One of the forward or rearward frame segments includes first and second stabilizing flanges that extend toward and slidably overlap opposing first and second sides of the other of the forward and rearward frame segments. The forward and rearward frame segments freely slide and pivot relative to each other during flexure of the base.
In a second preferred embodiment of the present invention, the frame of the skate includes a forward segment that mounts at least two forward wheels below the forefoot region of the base, and a rearward segment that mounts at least one rearward wheel below the heel region of the base, wherein the forward segment includes first and second stabilizing flanges that extend toward and slidably overlap or underlap the rearward frame segment, such that the at least two wheels will be in contact with the skating surface during the skater""s power stroke, and the forward and rearward frame segments remain longitudinally stable during flexure over the complete stroke.
In an alternate preferred embodiment to the present invention, the skate includes a frame secured to an underside of the base at the forefoot region of the base. The heel region of the base bears on the frame in a lower position, and elevates away from the frame to an upper position upon flexure of the base during skating. A guide is secured to one of the frame and the heel region of the base and projects toward and slidably engages the other of the frame and the heel region of the base during flexure of the base.
The present invention thus provides skates having bases that flex, preferably below the metatarsal head of the skater""s foot, in conformity with the anatomy of the foot. In a first preferred embodiment, the frame is split into two segments, which overlap each other for lateral stability, yet which freely and slidably pivot relative to each other during flexure. In an alternate embodiment, the heel of the shoe portion lifts away from the frame during flexure, and a guide is preferably provided that maintains lateral positioning of the upper relative to the frame during this movement. Thus the skates of the present invention provide for increased thrust during the skating stroke due to the ability to flex the foot, and concentrate flexing at the foot at the point most anatomically desirable and efficient. The preferred embodiments of the present invention include a biasing member, such as a spring plate, that pre-loads the heel of the skate in the lower position, such that after each stroke during skating, the heels snap back downwardly for full engagement with the frame and ground.